Message ID | 1426075692-19340-1-git-send-email-ghug@induct.be |
---|---|
State | Accepted |
Headers | show |
On Wed, Mar 11, 2015 at 01:08:12PM +0100, Gaetan Hug wrote: > The driver computes which clock divider it sould be using from the > requested period. This computation assumes that the link between the > register value and the actual divider value is raising 2 to the power of > the registry value. > > div = 1 << regvalue > > This is true only for the first 5 values out of 8. Next values are 64, > 256 and, 1024 - instead of 32, 64, 128. > This affects only the users requesting a period > 0.04369s. > > Replace the computation with a look-up table. > > Signed-off-by: Gaetan Hug <ghug@induct.be> > Acked-by: Shawn Guo <shawn.guo@linaro.org> > --- > drivers/pwm/pwm-mxs.c | 6 ++++-- > 1 file changed, 4 insertions(+), 2 deletions(-) Applied, though I made some last-minute changes, see below. > diff --git a/drivers/pwm/pwm-mxs.c b/drivers/pwm/pwm-mxs.c > index f75ecb0..c65e183 100644 > --- a/drivers/pwm/pwm-mxs.c > +++ b/drivers/pwm/pwm-mxs.c > @@ -35,6 +35,8 @@ > #define PERIOD_CDIV(div) (((div) & 0x7) << 20) > #define PERIOD_CDIV_MAX 8 > > +static unsigned const int cdiv[PERIOD_CDIV_MAX] = {1, 2, 4, 8, 16, 64, 256, 1024}; I turned this into static const unsigned int, which is the more canonical form and wrapped this over multiple lines so as not to exceed the 80-character limit. Thanks, Thierry
diff --git a/drivers/pwm/pwm-mxs.c b/drivers/pwm/pwm-mxs.c index f75ecb0..c65e183 100644 --- a/drivers/pwm/pwm-mxs.c +++ b/drivers/pwm/pwm-mxs.c @@ -35,6 +35,8 @@ #define PERIOD_CDIV(div) (((div) & 0x7) << 20) #define PERIOD_CDIV_MAX 8 +static unsigned const int cdiv[PERIOD_CDIV_MAX] = {1, 2, 4, 8, 16, 64, 256, 1024}; + struct mxs_pwm_chip { struct pwm_chip chip; struct clk *clk; @@ -54,13 +56,13 @@ static int mxs_pwm_config(struct pwm_chip *chip, struct pwm_device *pwm, rate = clk_get_rate(mxs->clk); while (1) { - c = rate / (1 << div); + c = rate / cdiv[div]; c = c * period_ns; do_div(c, 1000000000); if (c < PERIOD_PERIOD_MAX) break; div++; - if (div > PERIOD_CDIV_MAX) + if (div >= PERIOD_CDIV_MAX) return -EINVAL; }